Under the definitions of the International Telecommunications Union-Telecommunications Sector (ITU-T) Recommendation H.323 and related documents, it is assumed that the compliant communications endpoints contain all of the intelligence necessary to perform the protocols and procedures specified within these documents. Due to the complexity of these specifications, a significant computational power requirement is placed upon these endpoints. These current standards-based, protocol and procedure signaling methods may be described as complex. The protocols are state driven with both a large set of states and a large set of state transitions. Additionally, the protocols generally include a large set of messages and a large set of message elements.
If the endpoint is a computer-based workstation, processing the state-based protocols may be satisfied with relative ease. If the endpoints are not computer-based workstations, however, processing the state-based protocols typically dictates the inclusion of a relatively high-powered and expensive computer processor in combination with a dedicated device, known as a low-capability client. Typically, the low-capability client uses stateless messaging which is generally less complex having both limited messages and limited message elements. The actual functionality of the low-capability client does not otherwise require processor-based intelligence to perform its principle tasks or functions. Employing intelligence such as a processor with the low-capability client increases both the cost and design complexity as well as the requirements to meet other constraints on the system such as radiated emissions or temperature environments.
As the ITU-T Recommendation H.323 and related recommendations evolve, a higher and higher burden will be placed upon the low-capability clients such that they may remain interoperable with other computer-based workstations. Current methods for telephony signaling over Internet Protocol (IP) networks using ITU-T Recommendation H.323 protocols are typically rich in depth and scope of features. Rapid evolvement of the industry is driving a constant modification of current methods as well as the development of new methods.
As a consequence, the fundamental issues associated with deploying telephony over IP networks include difficulty in adapting to and supporting new and changing signaling methods at client devices, particularly as the number of clients increases. Additionally, added complexity along with the associated escalating cost of supporting the various signaling methods at a telephony client device further raises the costs, even though cost is expected to remain low.
An additional deficiency in the low-capability clients is the provision of services, such as call forwarding or voice messaging, for devices that are not on-line. Currently, the end station must supply all of the required features. If the end station is not functional at the time these features are requested, either through alternate usage or because it is powered down, then these vital communications features are not provided.
A proxy device may be defined as one that acts for or in the interest of an end station or remote terminal device. Proxy devices for data communications equipment exist today. For example, a File Transfer Protocol (FTP) proxy device, resident at the firewall boundary between an enterprise intranet and an external internet, allows an internet-based user with an FTP client to conduct an FTP session with an intranet-based server through the FTP proxy device. In the case of data communications protocols, the FTP proxy does not extend services to the intranet client. It merely forwards a request for action to the intranet client. The intranet server must have an FTP server application present and active in order to communicate with the calling internet client. Thus, the FTP proxy in this example does not fully act on behalf of the called internet client.
Generally, in the case of audio or audio-video client terminals rather than data terminals, there is currently no system which defines the behavior of an audio or audio-video communications protocol proxy which can act on the behalf of the called audio or audio-video terminals and deliver services, especially when the called terminal is not functional.
Accordingly, what is needed in the art is a system and method that accommodates a low-capability client whereby interactions and other control services may be performed in a centralized environment on behalf of the low-capability client.